The invention relates to a casting arrangement for metallic melts.
In the case of the slider closures of pouring ladles and intermediate vessels for the pouring metallic melts, such as are shown in the U.S. Pat. No. 4,076,153, of Bernard Tinnes, isued Feb. 28, 1978, workers in the art have been striving for some time to meet the danger of solidification of the melt in the discharge channel or of the freezing of the slider closure. At the same time, measures have already become known which attempt to prevent the penetration of melt into the discharge channel prior to the pouring. For this purpose, the discharge channel in the case of an empty vessel is filled either with a nonmetallic filling mass or with a metal with a low melting point.
Apart from the expenditure of work represented by these known measures, the are effective only as long as the pouring has not yet started. It is also not possible to prevent the filling mass or the filling metal from reaching, for example, the permanent mold and there has a disturbing effect.
In order to be able to avoid not only prior to the tapping but also during the pouring or operational interruptions of a shorter duration, the freezing of the discharge channel of a pouring vessel equipped with a slider closure, it has likewise been known to blow gas into the discharge channel in the closed state of the slider, for example, an inert gas. Apertures for the entry of gas into the discharge channel are at the same time provided either directly in the perforated brick or in the perforated brick casing in the fixed bottom plate of the slide or in the movable slider plate itself, whereby in the latter case, the entry opening for the gas is connected with the discharge channel only in the closed slider position.
By the blowing-in of gas, one strives to stir the melt located in the discharge channel in order to mix colder melt with warmer melt and in order thereby to prevent solidification or delay it. As a rule, the blowing-in of air or other not-inert gases, as well as nitrogen, is prohibited for metallurgical reasons and therefore expensive, inert gas must be used. As a result of the blowing-in of gas, there will be not only increased operating costs, but the melt will also be cooled down by the entering cold gas. In addition, there is the danger that because of the active withdrawal of heat by the gas flow and to be sure both from the melt located in the discharge channel as well as from the fire-resistant material limiting this discharge channel and an insufficient supply of heat from the casting vessel, a sudden freezing will take place, for example, because of insufficient stirring.
The fact that the entry of gas into the discharge channel presupposes apertures or pores in these limiting fire-resistant parts, forces one during the operation to operate at any time with a higher gas pressure than the ferrostatic pressure in the discharge channel. This ferrostatic pressure, however, varies considerably with the level of the melt in the casting vessel, so that the effect of the blowing-in of gas changes to an impermissible extent, depending on the melt level or filling state. If, on the other hand, the pressure of the gas is not sufficient, then there is the danger of plugging-up the apertures or pores for the feeding of the gas. The corresponding parts will then have to be replaced before they would have to be exchanged for reasons of wear. This has a particularly unfavorable effect on the operating costs, which are already burdened by the use of inert gas, because of the more expensive parts needed for the blowing-in of gas.